Cleanup

- Rename and move the variable to variables file
- Move code to the grid file
- Use the mixin to generate our own classes
- Wrap in a grid classes enabled conditional
- Document the mixin

scss/_card.scss

@@ -168,18 +168,6 @@
   }
 }
 
-$row-columns: 6 !default;
-
-@each $breakpoint in map-keys($grid-breakpoints) {
-  $infix: breakpoint-infix($breakpoint, $grid-breakpoints);
-
-  @for $i from 1 through $row-columns {
-    .row-cols#{$infix}-#{$i} > [class^="col"] {
-      flex: 0 0 calc(100% / #{$i});
-    }
-  }
-}
-
 
 //
 // Card groups

scss/_grid.scss

@@ -46,6 +46,16 @@
     @include make-row();
   }
 
+  @each $breakpoint in map-keys($grid-breakpoints) {
+    $infix: breakpoint-infix($breakpoint, $grid-breakpoints);
+
+    @for $i from 1 through $grid-row-columns {
+      .row-cols#{$infix}-#{$i} {
+        @include row-cols($i);
+      }
+    }
+  }
+
   // Remove the negative margin from default .row, then the horizontal padding
   // from all immediate children columns (to prevent runaway style inheritance).
   .no-gutters {

scss/_variables.scss

@@ -227,6 +227,7 @@ $container-max-widths: (
 
 $grid-columns:                12 !default;
 $grid-gutter-width:           30px !default;
+$grid-row-columns:            6 !default;
 
 
 // Components

scss/mixins/_grid.scss

@@ -49,3 +49,14 @@
   $num: $size / $columns;
   margin-left: if($num == 0, 0, percentage($num));
 }
+
+// Row columns
+//
+// Specify on a parent element(e.g., .row) to force immediate children into NN
+// numberof columns. Supports wrapping to new lines, but does not do a Masonry
+// style grid.
+@mixin row-cols($count) {
+  & > [class^="col"] {
+    flex: 0 0 calc(100% / #{$count});
+  }
+}

site/docs/4.3/layout/grid.md

@@ -381,6 +381,20 @@ Use these row columns classes to quickly create basic grid layouts or to control
 {% include example.html content=example %}
 </div>
 
+You can also use the accompanying Sass mixin, `row-cols()`:
+
+{% highlight scss %}
+.element {
+  // Three columns to start
+  @include row-cols(3);
+
+  // Five columns from medium breakpoint up
+  @include media-breakpoint-up(md) {
+    @include row-cols(5);
+  }
+}
+{% endhighlight %}
+
 ## Alignment
 
 Use flexbox alignment utilities to vertically and horizontally align columns. **Internet Explorer 10-11 do not support vertical alignment of flex items when the flex container has a `min-height` as shown below.** [See Flexbugs #3 for more details.](https://github.com/philipwalton/flexbugs#flexbug-3)